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1.
A facile approach to synthesize porous disordered carbon layers as energy storage units coating on graphene sheets to form interconnected frameworks by one‐step pyrolysis of the mixture of graphene oxide/polyaniline and KOH is presented. As effective energy storage units, these porous carbon layers play an important role in enhancing the electrochemical performances. The obtained porous carbon material exhibits a high specific surface area (2927 m2 g?1), hierarchical interconnected pores, moderate pore volume (1.78 cm3 g?1), short ion diffusion paths, and a high nitrogen level (6 at%). It displays both unparalleled gravimetric (481 F g?1) and outstanding volumetric capacitance (212 F cm?3) in an aqueous electrolyte. More importantly, the assembled symmetrical supercapacitor delivers not only high gravimetric (25.7 Wh kg?1 based on total mass of electroactive materials) but also high volumetric energy densities (11.3 Wh L?1) in an aqueous electrolyte. Furthermore, the assembled asymmetric supercapacitor yields a maximum energy density up to 88 Wh kg?1, which is, to the best of our knowledge, the highest value so far reported for carbon//MnO2 asymmetric supercapacitors in aqueous electrolytes. Therefore, this novel carbon material holds great promise for potential applications in energy‐related technological fields.  相似文献   

2.
A facile one‐step hydrothermal co‐deposition method for growth of ultrathin Ni(OH)2‐MnO2 hybrid nanosheet arrays on three dimensional (3D) macroporous nickel foam is presented. Due to the highly hydrophilic and ultrathin nature of hybrid nanosheets, as well as the synergetic effects of Ni(OH)2 and MnO2, the as‐fabricated Ni(OH)2‐MnO2 hybrid electrode exhibits an ultrahigh specific capacitance of 2628 F g?1. Moreover, the asymmetric supercapacitor with the as‐obtained Ni(OH)2‐MnO2 hybrid film as the positive electrode and the reduced graphene oxide as the negative electrode has a high energy density (186 Wh kg?1 at 778 W kg?1), based on the total mass of active materials.  相似文献   

3.
Hierarchically porous nitrogen‐doped carbon (HPC)/polyaniline (PANI) nanowire arrays nanocomposites are synthesized by a facile in situ polymerization. 3D interconnected honeycomb‐like HPC was prepared by a cost‐effective route via one‐step carbonization using urea and alkali‐treated wheat flour as carbon precursor with a high specific surface area (1294 m2 g?1). The specific capacitances of HPC and HPC/PANI (with a surface area of 923 m2 g?1) electrode are 383 and 1080 F g?1 in 1 m H2SO4, respectively. Furthermore, an asymmetric supercapacitor based on HPC/PANI as positive electrode and HPC as negative electrode is successfully assembled with a voltage window of 0–1.8 V in 1 m Na2SO4 aqueous electrolyte, exhibiting high specific capacitance (134 F g?1), high energy density (60.3 Wh kg?1) and power density (18 kW kg?1), and excellent cycling stability (91.6% capacitance retention after 5000 cycles).  相似文献   

4.
Composites of polypyrrole (PPy) and Cladophora nanocellulose, reinforced with 8 μm‐thick chopped carbon filaments, can be used as electrode materials to obtain paper‐based energy‐storage devices with unprecedented performance at high charge and discharge rates. Charge capacities of more than 200 C g?1 (PPy) are obtained for paper‐based electrodes at potential scan rates as high as 500 mV s?1, whereas cell capacitances of ~60–70 F g?1 (PPy) are reached for symmetric supercapacitor cells with capacitances up to 3.0 F (i.e.,0.48 F cm?2) when charged to 0.6 V using current densities as high as 31 A g?1 based on the PPy weight (i.e., 99 mA cm?2). Energy and power densities of 1.75 Wh kg?1 and 2.7 kW kg?1, respectively, are obtained when normalized with respect to twice the PPy weight of the smaller electrode. No loss in cell capacitance is seen during charging/discharging at 7.7 A g?1 (PPy) over 1500 cycles. It is proposed that the nonelectroactive carbon filaments decrease the contact resistances and the resistance of the reduced PPy composite. The present straightforward approach represents significant progress in the development of low‐cost and environmentally friendly paper‐based energy‐storage devices for high‐power applications.  相似文献   

5.
A three‐component, flexible electrode is developed for supercapacitors over graphitized carbon fabric, utilizing γ‐MnO2 nanoflowers anchored onto carbon nanotubes (γ‐MnO2/CNT) as spacers for graphene nanosheets (GNs). The three‐component, composite electrode doubles the specific capacitance with respect to GN‐only electrodes, giving the highest‐reported specific capacitance (308 F g?1) for symmetric supercapacitors containing MnO2 and GNs using a two‐electrode configuration, at a scan rate of 20 mV s?1. A maximum energy density of 43 W h kg?1 is obtained for our symmetric supercapacitors at a constant discharge‐current density of 2.5 A g?1 using GN–(γ‐MnO2/CNT)‐nanocomposite electrodes. The fabricated supercapacitor device exhibits an excellent cycle life by retaining ≈90% of the initial specific capacitance after 5000 cycles.  相似文献   

6.
3D‐networked, ultrathin, and porous Ni3S2/CoNi2S4 on Ni foam (NF) is successfully designed and synthesized by a simple sulfidation process from 3D Ni–Co precursors. Interestingly, the edge site‐enriched Ni3S2/CoNi2S4/NF 3D‐network is realized by the etching‐like effect of S2? ions, which made the surfaces of Ni3S2/CoNi2S4/NF with a ridge‐like feature. The intriguing structural/compositional/componental advantages endow 3D‐networked‐free‐standing Ni3S2/CoNi2S4/NF electrodes better electrochemical performance with specific capacitance of 2435 F g?1 at a current density of 2 A g?1 and an excellent rate capability of 80% at 20 A g?1. The corresponding asymmetric supercapacitor achieves a high energy density of 40.0 W h kg?1 at an superhigh power density of 17.3 kW kg?1, excellent specific capacitance (175 F g?1 at 1A g?1), and electrochemical cycling stability (92.8% retention after 6000 cycles) with Ni3S2/CoNi2S4/NF as the positive electrode and activated carbon/NF as the negative electrode. Moreover, the temperature dependences of cyclic voltammetry curve polarization and specific capacitances are carefully investigated, and become more obvious and higher, respectively, with the increase of test temperature. These can be attributed to the components' synergetic effect assuring rich redox reactions, high conductivity as well as highly porous but robust architectures. This work provides a general, low‐cost route to produce high performance electrode materials for portable supercapacitor applications on a large scale.  相似文献   

7.
In this paper, a novel freestanding core‐branch negative and positive electrode material through integrating trim aligned Fe2O3 nanoneedle arrays (Fe2O3 NNAs) is first proposed with typical mesoporous structures and NiCo2O4/Ni(OH)2 hybrid nanosheet arrays (NiCo2O4/Ni(OH)2 HNAs) on SiC nanowire (SiC NW) skeletons with outstanding resistance to oxidation and corrosion, good conductivity, and large‐specific surface area. The original built SiC NWs@Fe2O3 NNAs is validated to be a highly capacitive negative electrode (721 F g?1 at 2 A g?1, i.e., 1 F cm?2 at 2.8 mA cm?2), matching well with the similarly constructed SiC NWs@NiCo2O4/Ni(OH)2 HNAs positive electrode (2580 F g?1 at 4 A g?1, i.e., 3.12 F cm?2 at 4.8 mA cm?2). Contributed by the uniquely engineered electrodes, a high‐performance asymmetric supercapacitor (ASC) is developed, which can exhibit a maximum energy density of 103 W h kg?1 at a power density of 3.5 kW kg?1, even when charging the device within 6.5 s, the energy density can still maintain as high as 45 W h kg?1 at 26.1 kW kg?1, and the ASC manifests long cycling lifespan with 86.6% capacitance retention even after 5000 cycles. This pioneering work not only offers an attractive strategy for rational construction of high‐performance SiC NW‐based nanostructured electrodes materials, but also provides a fresh route for manufacturing next‐generation high‐energy storage and conversion systems.  相似文献   

8.
Fullerene‐based carbons are promising electrode materials for supercapacitors due to their unique carbon structures and tunable architectures at the molecular level. By introducing various functional groups with many elements on the fullerene cages, diverse in situ metal/nonmetal‐doped carbon materials with enhanced pseudocapacitances and/or double layer capacitances can be prepared. In the present work, a fullerene derivative, ferrocenylpyrrolidine C60, containing nitrogen and iron, is chosen as the only precursor. A unique microstructure is fabricated by a liquid–liquid interfacial precipitation process. Subsequently, a facile, one‐step annealing of the microstructure at different temperatures is performed. A series of in situ N and Fe‐codoped laminated 3D hierarchical carbon composites in the shape of a cross are successfully synthesized. The as‐prepared N and Fe‐codoped carbon material treated at 700 °C exhibits a high specific capacitance of 505.4 F g?1 at 0.1 A g?1. To the best knowledge, this is the highest supercapacitor capacitance based on fullerene electrode materials. The use of a fullerene derivative as an in‐situ doped carbon for applications in energy storage opens a new avenue for developing future synthetic strategies to extend the repertoire of electrode materials with high performance.  相似文献   

9.
Layered hydroxides (LHs) are promising supercapacitor electrode materials with high specific capacitances. However, they generally exhibit poor energy storage ability at high current densities due to their insulating nature. Nickel‐cobalt‐aluminum LHs are synthesized and chemically treated to form LHs with enhanced conductivity that results in greatly enhanced rate performances. The key role of chemical treatment is to enable the partial conversion of Co2+ to a more conductive Co3+ state that stimulates charge transfers. Simultaneously, the defects on the LHs caused by the selective etching of Al promoted the electrolyte diffusion within LHs. As a result, the LHs show a high specific capacitance of 738 F g?1 at 30 A g?1, which is 57.2% of 1289 F g?1 at 1 A g?1. The strategy provides a facile and effective method to achieve high performance LHs for supercapacitor electrode materials.  相似文献   

10.
Flexible fiber‐shaped supercapacitors have shown great potential in portable and wearable electronics. However, small specific capacitance and low operating voltage limit the practical application of fiber‐shaped supercapacitors in high energy density devices. Herein, direct growth of ultrathin MnO2 nanosheet arrays on conductive carbon fibers with robust adhesion is exhibited, which exhibit a high specific capacitance of 634.5 F g?1 at a current density of 2.5 A g?1 and possess superior cycle stability. When MnO2 nanosheet arrays on carbon fibers and graphene on carbon fibers are used as a positive electrode and a negative electrode, respectively, in an all‐solid‐state asymmetric supercapacitor (ASC), the ASC displays a high specific capacitance of 87.1 F g?1 and an exceptional energy density of 27.2 Wh kg?1. In addition, its capacitance retention reaches 95.2% over 3000 cycles, representing the excellent cyclic ability. The flexibility and mechanical stability of these ASCs are highlighted by the negligible degradation of their electrochemical performance even under severely bending states. Impressively, as‐prepared fiber‐shaped ASCs could successfully power a photodetector based on CdS nanowires without applying any external bias voltage. The excellent performance of all‐solid‐state ASCs opens up new opportunity for development of wearable and self‐powered nanodevices in near future.  相似文献   

11.
To push the energy density limit of supercapacitors, a new class of electrode materials with favorable architectures is strongly needed. Binary metal sulfides hold great promise as an electrode material for high‐performance energy storage devices because they offer higher electrochemical activity and higher capacity than mono‐metal sulfides. Here, the rational design and fabrication of NiCo2S4 nanosheets supported on nitrogen‐doped carbon foams (NCF) is presented as a novel flexible electrode for supercapacitors. A facile two‐step method is developed for growth of NiCo2S4 nanosheets on NCF with robust adhesion, involving the growth of Ni‐Co precursor and subsequent conversion into NiCo2S4 nanosheets through sulfidation process. Benefiting from the compositional features and 3D electrode architectures, the NiCo2S4/NCF electrode exhibits greatly improved electrochemical performance with ultrahigh capacitance (877 F g?1 at 20 A g?1) and excellent cycling stability. Moreover, a binder‐free asymmetric supercapacitor device is also fabricated by using NiCo2S4/NCF as the positive electrode and ordered mesoporous carbon (OMC)/NCF as the negative electrode; this demonstrates high energy density (≈45.5 Wh kg?1 at 512 W kg?1).  相似文献   

12.
CuO and Cu2O are non‐noble transition metal oxide supercapacitive materials with high theoretical specific capacitances above 1800 F g?1. In this work, by adjusting organic additives of a colloidal system, Cu, Cu2O, and CuO are grown in situ on nickel foam. CuO exhibits a specific capacitance of 1355 F g?1 at 2 A g?1 in 3 m KOH, a value well above those of Cu and Cu2O (<500 F g?1), and is superior to other known CuO electrodes. The CuO electrode exhibits 70% of its initial capacity, and the Columbic efficiency remains ≈100% after 7000 cycles at 4 A g?1. Cu2O exhibits the worst electrochemical performance, mainly due to the inactive barrier layer forming on the surface. This work provides an efficient synthetic platform for both comparable supercapacitive studies and cost‐effective electrochemical energy storage applications.  相似文献   

13.
Nanoporous carbons (NPCs) with engineered specific pore sizes and sufficiently high porosities (both specific surface area and pore volume) are necessary for storing energy in the form of electric charges and molecules. Herein, NPCs, derived from biomass pine‐cones, coffee‐grounds, graphene‐oxide and metal‐organic frameworks, with systematically increased pore width (<1.0 nm to a few nm), micropore volume (0.2–0.9 cm3 g?1) and specific surface area (800–2800 m2 g?1) are presented. Superior CO2, H2, and H2O uptakes of 35.0 wt% (≈7.9 mmol g?1 at 273 K), 3.0 wt% (at 77 K) and 85.0 wt% (at 298 K), respectively at 1 bar, are achieved. At controlled microporosity, supercapacitors deliver impressive performance with a capacity of 320 and 230 F g?1 at 500 mA g?1, in aqueous and organic electrolytes, respectively. Excellent areal capacitance and energy density (>50 Wh kg?1 at high power density, 1000 W kg?1) are achieved to form the highest reported values among the range of carbons in the literature. The noteworthy energy storage performance of the NPCs for all five cases (CO2, H2, H2O, and capacitance in aqueous and organic electrolytes) is highlighted by direct comparison to numerous existing porous solids. A further analysis on the specific pore type governed physisorption capacities is presented.  相似文献   

14.
A simple and scalable method to fabricate a yarn‐type supercapacitor with a large specific capacitance without the aid of traditional pseudocapacitive electrode materials such as conducting polymers and metal oxides is reported. The yarn‐type supercapacitors are made from twisting reduced graphene oxide (rGO) or/and single‐walled carbon nanotubes (SWNTs)‐coated Korean traditional paper (KTP). The yarn‐type paper supercapacitor displays surprisingly enhanced electrochemical capacitance values, showing synergistic effect between rGO and SWNTs (500 times larger than performance of yarn‐type rGO‐coated paper supercapacitors). Coating rGO or/and SWNTs on KTP gives good morphology to the composite film, in which porosity increases and mean pore diameter decreases. The yarn‐type rGO/SWNT paper supercapacitor shows good mechanical strength, high flexibility, excellent electrochemical performance, and long‐life operation. The yarn‐type supercapacitor has an excellent electrochemical performance with a specific capacitance of 366 F g?1 at scan rate of 25 mV s?1 and high stability without any degradation in electrical performance up to 10 000 charge–discharge cycles. The average capacitance of rGO/SWNT@KTP yarn‐type supercapacitors is seven times higher than that of sheet‐type supercapacitors at scan rate of 500 mV s?1. The lighting of a red light‐emitting diode (LED) is demonstrated by the yarn‐type paper supercapacitor without connecting supercapacitors in series.  相似文献   

15.
Manganese oxide/carbon aerogel composite electrodes are prepared by a self‐limiting anodic‐electrochemical deposition of manganese oxide into a binder‐enriched carbon aerogel layer, drop‐cast on a graphite substrate, using 0.1 M Mn(CH3COO)2·4H2O as the electrolyte. Manganese oxide grows in the form of thin nanofibers along the backbone of the carbon aerogel, leaving adequate working space for the electrolyte and enabling a fuller extent of the utilization of the manganese oxide to make the composite an outstanding supercapacitor electrode material. The manganese oxide is determined to be Mn3O4 with the Raman spectroscopy and high‐resolution transmission electron microscopy. The rectangularity of the cyclic‐voltammogram loops of the composite electrode is excellent and remains that way for scan rates up to a very‐high value of 500 mV s?1, indicating extremely good redox reversibility and cycle efficiency. At a scan rate of 25 mV s?1, the specific capacitance, as measured in 0.5 M Na2SO4 for a potential window of 0.1–0.9 V vs. Ag/AgCl, reaches a maximum value of 503 F g?1 and experiences only a negligible decay of less than 1% at the 6000th cycle, implying an extraordinary cycling stability. The cycling efficiency is as high as 98% at a current density of 8 A g?1 cm?2, showing an almost‐ideal capacitive behavior. The power density reaches 48.5 kW kg?1 and the energy density 21.6 W h kg?1 at a scan rate of 500 mV s?1, well above the specifications of current state‐of‐the‐art supercapacitors.  相似文献   

16.
Unique nanostructures always lead to extraordinary electrochemical energy storage performance. Here, the authors report a new strategy for using Metal‐organic frameworks (MOFs) derived cobalt sulfide in a carbon matrix with a 3D honeycombed porous structure, resulting in a high‐performance supercapacitor with unrivalled capacity of ≈1887 F g‐1 at the current density of 1 A g‐1. The honeycomb‐like structure of Co9S8@C composite is loosely adsorbed, with plentiful surface area and high conductivity, leading to improved Faradaic processes across the interface and enhanced redox reactions at active Co9S8 sites. Therefore, the heterostructure‐fabricated hybrid supercapacitor, using activated carbon as the counter electrode, demonstrates a high energy density of 58 Wh kg‐1 at the power density of 1000 W kg‐1. Even under an ultrahigh power density of 17 200 W kg‐1, its energy density maintains ≈38 Wh kg‐1. The hybrid supercapacitor also exhibits suitable cycling stability, with ≈90% capacity retention after 10 000 continuous cycles at the current density of 5 A g‐1. This work presents a practical method for using MOFs as sacrificial templates to synthesize metal‐sulfides for highly efficient electrochemical energy storage.  相似文献   

17.
Asymmetric supercapacitors featuring both high energy and power densities as well as a long lifespan are much sought after and may become a reality depending on the availability of cheap yet highly active electrode materials. Here, a novel flexible architecture electrode made of NiCoAl‐layered double hydroxide (NiCoAl‐LDH) nanoplates coupled with NiCo‐carbonate hydroxide (NiCo‐CH) nanowires, grown on graphite paper via an in situ, one‐step, hydrothermal method is reported. The nanowire‐like NiCo‐CH species in the nanoplate matrix function as a scaffold and support the dispersion of the NiCoAl‐LDH nanoplates, resulting in a relatively loose and open structure within the electrode matrix. Asymmetric supercapacitors fabricated using the nanohybrids as the positive electrode and a typical activated carbon (AC) as negative electrode show a high energy density of 58.9 Wh kg?1 at a power density of 0.4 kW kg?1, which is based on the total mass of active materials at a voltage of 1.6 V. An energy density of 14.9 Wh kg?1 can be retained even at a high power density of 51.5 kW kg?1. Our asymmetric supercapacitor also exhibits an excellent long cycle life, whereby a specific capacitance of 97% is retained even after 10 000 cycles.  相似文献   

18.
Potassium ion hybrid capacitors have great potential for large‐scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro‐sulfonyl)imide‐based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N‐doping carbon‐coated FeSe2 clusters are demonstrated as the anode material for a hybrid capacitor, delivering a reversible capacity of 295 mAh g?1 at 100 mA g?1 over 100 cycles and a high rate capability of 158 mAh g?1 at 2000 mA g?1 over 2000 cycles. Meanwhile, through density functional theory calculations, in situ X‐ray diffraction, and ex situ transmission electron microscopy, the evolution of FeSe2 to Fe3Se4 for the electrochemical reaction mechanism is successfully revealed. The battery‐supercapacitor hybrid using commercial activated carbon as the cathode and FeSe2/N‐C as the anode is obtained. It delivers a high energy density of 230 Wh kg?1 and a power density of 920 W kg?1 (the energy density and power density are calculated based on the total mass of active materials in the anode and cathode).  相似文献   

19.
In pursuing higher energy density, without compromising the power density of supercapacitor platforms, the application of an advanced 2D nanomaterial is utilized to maximize performance. Antimonene, for the first time, is characterized as a material for applications in energy storage, being applied as an electrode material as the basis of a supercapacitor. Antimonene is shown to significantly improve the energy storage capabilities of a carbon electrode in both cyclic voltammetry and galvanostatic charging. Antimonene demonstrates remarkable performance with a capacitance of 1578 F g?1, with a high charging current density of 14 A g?1. Hence, antimonene is shown to be a highly promising material for energy storage applications. The system also demonstrates a highly competitive energy and power densities of 20 mW h kg?1 and 4.8 kW kg?1, respectively. In addition to the excellent charge storing abilities, antimonene shows good cycling capabilities.  相似文献   

20.
Highly porous carbide‐derived carbon (CDC) mesofoams (DUT‐70) are prepared by nanocasting of mesocellular silica foams with a polycarbosilane precursor. Ceramic conversion followed by silica removal and high‐temperature chlorine treatment yields CDCs with a hierarchical micro‐mesopore arrangement. This new type of polymer‐based CDC is characterized by specific surface areas as high as 2700 m2 g?1, coupled with ultrahigh micro‐ and mesopore volumes up to 2.6 cm3 g?1. The relationship between synthesis conditions and the properties of the resulting carbon materials is described in detail, allowing precise control of the properties of DUT‐70. Since the hierarchical pore system ensures both efficient mass transfer and high capacities, the novel CDC shows outstanding performance as an electrode material in electrochemical double‐layer capacitors (EDLCs) with specific capacities above 240 F g?1 when measured in a symmetrical two‐electrode configuration. Remarkable capacities of 175 F g?1 can be retained even at high current densities of 20 A g?1 as a result of the enhanced ion‐transport pathways provided by the cellular mesostructure. Moreover, DUT‐70 can be infiltrated with sulfur and host the active material in lithium–sulfur battery cathodes. Reversible capacities of 790 mAh g?1 are achieved at a current rate of C/10 after 100 cycles, which renders DUT‐70 an ideal support material for electrochemical energy‐storage applications.  相似文献   

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